Repeated electrical or mechanical operations affect the surface of photosensitive bodies used in electrophotographic applications. Examples of such operations include cleaning, transfer, and image development processes; or roller electrical charging, corona electrical charging, and other electrical charging processes. Because the surface of photosensitive bodies is subjected to wear and undergoes degradation due to friction and such during cleaning and electrical charging, there is a demand for improvements in terms of the durability of photosensitive bodies.
Attempts to improve characteristics by reducing surface energy are known in the art. For example, attempts to reduce surface energy have been made by adding polydimethylsiloxane oils or silicone oils and other polysiloxane resins, such as polytetrafluoroethylene to the photosensitive layer to increase the durability of photosensitive bodies.
A protective layer may be formed on the surface of photosensitive bodies. For example, JP-A-57-30843 (1982) discloses using coating materials obtained by dispersing electrically conductive particles in various resins. JP-C-05-46940 (1993) discloses applying a surface-protecting layer of crosslinked polysiloxane to the surface of photosensitive bodies. The polysiloxane is composed of a product of joint hydrolytic condensation of a trifunctional alkoxysilane and a tetrafunctional alkoxysilane.
In electrophotographic processes, it is necessary to neutralize the electric charge on the surface of the photosensitive body with the electric charge generated in the charge generating layer, and the electric charge has to be transferred through the coating layer on the surface of the photosensitive body. Therefore, the coating materials must be electrically conductive. Electrical conductivity can be imparted to coating materials by dispersing in the coating material, carbon and particles of metals and metallic compounds, such as aluminum, copper, silver, gold, indium oxide, tin oxide, and the like. However, when such particles are dispersed, the formation of primary or secondary particles can cause light scattering that causes a decrease in sensitivity and image degradation.
One object of this invention is to provide a process for the preparation of an electrically conductive coating material that forms a protective layer of polysiloxane for electrophotographic photosensitive bodies. A further object of this invention is to produce a coating material that has superior optical homogeneity and is not detrimental to the functionality of the electrophotographic photosensitive bodies.